The present invention relates to a vented case for holding contact lenses that is capable of venting gases from the case interior as chemical reactions proceed therein during disinfecting, cleaning or storing of the lenses in contact with a treating solution. More particularly, the invention relates to a contact lens case that is capable of adequately venting oxygen from said case during neutralization of a hydrogen peroxide disinfecting solution.
Maintenance of contact lenses typically requires immersion in various cleaning, disinfecting or storage solutions. A number of maintenance processes involve chemical reactions which may involve the generation of gaseous by-products. For example, contact lenses are conventionally disinfected by contacting them with a dilute solution of hydrogen peroxide. At the completion of the disinfecting process lenses must be freed of any residual hydrogen peroxide. A number of regimens for this purpose involve catalytic decomposition of the hydrogen peroxide with evolution of oxygen. The agent for decomposing the hydrogen peroxide may be a metal catalyst or an enzyme such as catalase. The hydrogen peroxide disinfecting solution must typically contact the decomposing or neutralizing agent for a significant period of time to completely decompose the hydrogen peroxide. Thus, the container holding the lenses and solution is preferably continuously vented to permit the gases to vent from the container to the environment rather than risk fracture or rupture of the container through buildup of excessive gas pressure. A number of prior workers describe various systems and mechanisms for releasing and venting gas pressure from lens cases.
Iba et al in U.S. Pat. No. 5,143,104 describe a vented lens case in which gas vents through a rather complexly formed grooved and multiple aperture cap in combination with an impermeable membrane that includes an H-shaped perforation that acts as a one-way valve to vent gas while preventing liquid from discharging from the container. Su et al in U.S. Pat. No. 4,889,693 describe a deformable plug that functions as a one-way valve when pressure in the case sufficiently deforms the plug.
In U.S. Pat. No. 4,637,919, Ryder et al describe a vented case, again of a rather complex nature, that includes an apertured cap fitted with a plug that includes a semi-permeable membrane for ventage. In LaBoeuf U.S. Pat. No. 4,396,583, a vented case is described having a cap including a cavity for supporting a vapor-permeable, liquid-impermeable barrier through which gas is vented.
Each of the prior systems involves relatively complex structures, increasing the costs of the device, as well as adding to the difficulty of manufacture. In addition, many of the prior art cases leak when upset. It is desirable to provide a simplified venting system, yet provide effective venting of gas without significant discharge of fluid, particularly, for example, if the case should be upset during transport.